Abstract
Gated terahertz cyclotron resonance measurements on epitaxial BiSe thin films capped with InSe enable the first spectroscopic characterization of a single topological interface state from the vicinity of the Dirac point to above the conduction band edge. A precipitous drop in the scattering rate with Fermi energy is observed, which is interpreted as the surface state decoupling from bulk states and evidence of a shift of the Dirac point towards mid-gap. Near the Dirac point, potential fluctuations of 50 meV are deduced from an observed loss of differential optical spectral weight near the Dirac point. Potential fluctuations are reduced by a factor of two at higher surface Fermi levels in the vicinity of the conduction band edge inferred from the width of the scattering rate step. The passivated topological interface state attains a high mobility of 3500 cm/V s near the Dirac point.
- Received 18 August 2012
DOI:https://doi.org/10.1103/PhysRevB.87.155126
©2013 American Physical Society